Study of zeolite influence on analytical characteristics of urea biosensor based on ion-selective field-effect transistors

A possibility of the creation of potentiometric biosensor by adsorption of enzyme urease on zeolite was investigated. Several variants of zeolites (nano beta, calcinated nano beta, silicalite, and nano L) were chosen for experiments. The surface of pH-sensitive field-effect transistors was modified with particles of zeolites, and then the enzyme was adsorbed. As a control, we used the method of enzyme immobilization in glutaraldehyde vapour (without zeolites). It was shown that all used zeolites can serve as adsorbents (with different effectiveness). The biosensors obtained by urease adsorption on zeolites were characterized by good analytical parameters (signal reproducibility, linear range, detection limit and the minimal drift factor of a baseline). In this work, it was shown that modification of the surface of pH-sensitive field-effect transistors with zeolites can improve some characteristics of biosensors

Elaboration of Urease Adsorption on Silicalite for Biosensor Creation

A possibility of efficient urease adsorption on silicalite for the purpose of biosensor creation was investigated. The procedure of urease adsorption on silicalite is notable for such advantages as simple and fast performance and non-use of toxic or auxiliary compounds. Optimal conditions for modifying transducer surfaces with silicalite and subsequent urease adsorption on these surfaces were selected. The working parameters of the created biosensor were optimized. The developed biosensor with adsorbed urease was characterized by good intra-reproducibility (RSD 4.5?%), improved inter-reproducibility (RSD of urea determination is 9?%) and operational stability (less than 10?% loss of activity after 10 days). Besides, the developed method for enzyme adsorption on silicalite was compared with the traditional methods of urease immobilization in biosensorics. Working conditions of the produced biosensor (pH and ionic strength) were shown to be close to those of the biosensor based on urease immobilized in GA vapor. For these reasons, it was concluded that the method of enzyme adsorption on silicalite is well-suited for biosensor standardization aimed at its further manufacture

APPLICATION OF GLUTAMATE-SENSITIVE BIOSENSOR FOR ANALYSIS OF FOODSTUFF

The aim of the work were the optimization of an amperometric glutamate-sensitive biosensor and its utilization for the determination of the glutamate concentrations in food samples. Amperometric method of measurements was used. The biosensor was based on immobilized glutamate oxidase and platinum disc electrode. The biosensor was connected to the working cell with auxiliary (platinum wire) and reference (Ag/AgCl) electrodes. The biosensor exhibited high sensitivity to glutamate, duration of one analysis was about 5 min. An influence of the ionic strength, pH, and buffer capacity on the biosensor operation was investigated. The sensitivity of biosensor to various possible interfering substances, including amino acids, was studied; high selectivity to glutamate was shown. The reproducibility of analysis of food samples and an impact of sample dilution was evaluated. Glutamate concentrations in different sauces and seasonings were measured by the developed biosensor; the results correlated well with those obtained by the spectrophotometric method (R2 = 0,988). Thus, the amperometric biosensor for glutamate determination was successfully optimized and used for measurement of glutamate concentrations in sauces and seasonings

Influence of Composition of Zeolite/Enzyme Nanobiocomposites on Analytical Characteristics of Urea Biosensor Based on Ion-Selective Field-Effect Transistors

Zeolite/enzyme nanobiocomposites of different compositions were tested in this work for the improvement of biosensor analytical characteristics. The bioselective element based on urease immobilized by cross-linking with glutaraldehyde was used as a model. The working characteristics of biosensors based on various zeolite/enzyme nanocomposites were examined and compared with those of urease-based biosensors. An optimal concentration of zeolytes beta (BEA) in bioselective elements is determined to be 1.5%. It ensures as wide linear range of measurement without remarkable loss in biosensor sensitivity to urea. The BEA zeolite-based biosensors were shown to have better working parameters in comparison with those based on zeolites A (LTA). A decrease in biosensor sensitivity to heavy metal ions was demonstrated for all zeolites used, which testifies to probable increase in stability of urea measurement in real environmental samples

Development of novel enzyme potentiometric biosensor based on pH-sensitive field-effect transistors for aflatoxin B1 analysis in real samples

International audienceThis study aimed at the development and optimization of a potentiometric biosensor based on pH-sensitive field-effect transistors and acetylcholinesterase for aflatoxin B1 determination in real samples. Optimal conditions for bioselective elements operation were defined and analytical characteristics of the proposed biosensor were studied. The proposed biosensor characterized high operational stability and reproducibility of signal. Selectivity of acetylcholinesterase-biosensor to aflatoxins in relation to other groups of toxic substances was analyzed. The developed biosensor was applied to the determination of aflatoxin B1 in real samples (sesame, walnut and pea)

Development of Silicalite/Glucose Oxidase-Based Biosensor and Its Application for Glucose Determination in Juices and Nectars

The application of silicalite for improvement of enzyme adsorption on new stainless steel electrodes is reported. Glucose oxidase (GOx) was immobilized by two methods: cross-linking by glutaraldehyde (GOx-GA) and cross-linking by glutaraldehyde along with GOx adsorption on silicalite-modified electrode (SME) (GOx-SME-GA). The GOx-SME-GA biosensors were characterized by a four- to fivefold higher sensitivity than GOx-GA biosensor. It was concluded that silicalite together with GA sufficiently enhances enzyme adhesion on stainless steel electrodes. The developed GOx-SME-GA biosensors were characterized by good reproducibility of biosensor preparation (relative standard deviation (RSD)—18 %), improved signal reproducibility (RSD of glucose determination was 7 %), and good storage stability (29 % loss of activity after 18-day storage). A series of fruit juices and nectars was analyzed using GOx-SME-GA biosensor for determination of glucose concentration. The obtained results showed good correlation with the data of high-performance liquid chromatography (HPLC) (R = 0.99)